1. Field of the Disclosure
The present invention relates to liquid crystal display devices, and more particularly, to a method for analyzing a light profile of a light source for reducing capacity of a memory which is to store light profile data and device and method for driving local dimming of a liquid crystal display device by using the same.
2. Discussion of the Related Art
Recently, as a picture display device, flat display devices, such as a liquid crystal display device LCD, a plasma display panel PDP, an organic light emitting diode OLED, and the like are used, mainly.
The liquid crystal display device is provided with a liquid crystal panel for displaying a picture with a pixel matrix which utilizes electric and optical characteristics of liquid crystals having anisotropy, such as refractive index and a dielectric constant, a driving circuit for driving the liquid crystal panel, and a backlight unit for irradiating a light to the liquid crystal panel. Each pixel of the liquid crystal display device controls transmissivity of the light passing through the liquid crystal panel and a polarization plate from the backlight unit by varying a direction of arrangement of the liquid crystal in response to a data signal, for producing gradation.
Brightness of each pixel of the liquid crystal display device is brightness of the backlight unit multiplied by the light transmissivity of the liquid crystals. For improvement of a contrast ratio and reducing power consumption, the liquid crystal display device uses backlight dimming in which a received picture is analyzed to adjust a dimming value for controlling the brightness of the backlight unit and making data compensation. For an example, the backlight dimming reduces the backlight brightness by reducing the dimming value, and increases the brightness by making the data compensation, thereby reducing the power consumption.
Recently, the backlight unit uses an LED backlight in which light emitting diodes (hereafter, LED) are used as a light source which has advantages of high brightness and low power consumption. Since the LED backlight unit enables control of each position, the LED backlight unit can be driven by a local dimming in which the backlight is divided into a plurality of light emission blocks for controlling the brightness block by block. The local dimming can improve the contrast ratio further and reduce the power consumption further since the local dimming divides the backlight unit and the liquid crystal panel into a plurality of blocks respectively, analyzes the data on a block-by-block basis to determine a local dimming value and make data compensation.
Since the local dimming divides the backlight unit into the plurality of light emission blocks and controls brightness of the backlight unit on the block-by-block basis, reducing whole brightness of the backlight unit lower than the global dimming, input data is compensated for the local dimming at the time of the local dimming. The local dimming compensates the data by measuring a light profile of a light source of each block, storing the light profile to a memory, and analyzing the light profile stored thus to determine a quantity of a light which reaches to each pixel.
However, the related art local dimming has a problem in that a substantially large memory is required because brightness data of all pixels at a light emission region are stored as the light profile data on each of the light blocks.